From 2d6b09b66a0fea7412ab40002cdce4eb02da2854 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=90=B4=E7=83=A8?= <wuye@bszhihui.com>
Date: Wed, 10 Aug 2022 11:19:58 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200024.=E4=B8=A4=E4=B8=A4?=
 =?UTF-8?q?=E4=BA=A4=E6=8D=A2=E9=93=BE=E8=A1=A8=E4=B8=AD=E7=9A=84=E8=8A=82?=
 =?UTF-8?q?=E7=82=B9=20PHP=E7=89=88=E6=9C=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../0024.两两交换链表中的节点.md    | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/problems/0024.两两交换链表中的节点.md b/problems/0024.两两交换链表中的节点.md
index 4b4b39e7..5b73fb05 100644
--- a/problems/0024.两两交换链表中的节点.md
+++ b/problems/0024.两两交换链表中的节点.md
@@ -336,5 +336,48 @@ object Solution {
 }
 ```
 
+PHP:
+```php
+//虚拟头结点
+function swapPairs($head) {
+    if ($head == null || $head->next == null) {
+        return $head;
+    }
+
+    $dummyNode = new ListNode(0, $head);
+    $preNode = $dummyNode; //虚拟头结点
+    $curNode = $head;
+    $nextNode = $head->next;
+    while($curNode && $nextNode) {
+        $nextNextNode = $nextNode->next; //存下一个节点
+        $nextNode->next = $curNode; //交换curHead 和 nextHead
+        $curNode->next = $nextNextNode;
+        $preNode->next = $nextNode; //上一个节点的下一个指向指向nextHead
+
+        //更新当前的几个指针
+        $preNode = $preNode->next->next;
+        $curNode = $nextNextNode;
+        $nextNode = $nextNextNode->next;
+    }
+
+    return $dummyNode->next;
+}
+
+//递归版本
+function swapPairs($head)
+{
+    // 终止条件
+    if ($head === null || $head->next === null) {
+        return $head;
+    }
+
+    //结果要返回的头结点
+    $next = $head->next;
+    $head->next = $this->swapPairs($next->next); //当前头结点->next指向更新
+    $next->next = $head;  //当前第二个节点的->next指向更新
+    return $next;  //返回翻转后的头结点
+}
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>